I have blond hair and black eyebrows (and lashes, etc.) I have Finnish, French, German, and Irish in my background. My Dad was born a tow-head (white blond) and has black hair now. People are just weird.

Hmm… maybe:
1.) He dyed his hair… since he was, like, 8? Cause it’s blond in his flashbacks, too.
2.) He stands in the sun waaaay too much.
3.) He’s Jesus.
4.) He’s Batman.
or 5.) This is all CGI and the artist can do whatever he wants without having any proper reason. Seriously, there’s mermaids and fairies and rock giants. I think we can let different colored eyebrows slide.